Multi-Objective Design Optimisation of Inlet and Combustor for Axisymmetric Scramjets

Scramjet airbreathing propulsion is a promising technology for efficient and economical access-to-space. Flow compression in the inlet and fuel combustion in the combustor play a major role in scramjet mechanism, their efficiencies crucially influencing the overall scramjet performance. A double-objective shape optimisation for an axisymmetric inlet and combustor configuration using hydrogen as fuel premixed into air has been performed for minimum total pressure loss and maximum combustion efficiency in the present study. A state-of-the-art MDO (multi-objective design optimisation) capability with surrogate-assisted evolutionary algorithms has been employed, coupled with a CFD solver for inviscid flowfields involving chemical reactions represented by Evans & Schexnayder's model. The obtained Pareto optimal front suggests the possibility of substantial improvement in efficiency and the counteracting nature of the two objective functions. Geometries with higher combustion efficiency are characterised by a higher compression inlet with larger leading-edge radius and a longer combustor, whereas opposite trends are observed for configurations with smaller total pressure loss.